The Best Time of Day to Exercise
The Best Time of Day to Exercise
Men at risk for diabetes had greater blood sugar control and lost more belly fat when they exercised in the afternoon than in the morning.
Is it better for our bodies to work out at certain times of day?
A useful new study of exercise timing and metabolic health suggests that, at least for some people, the answer is a qualified yes. The study, which looked at men at high risk for Type 2 diabetes, found that those who completed afternoon workouts upped their metabolic health far more than those who performed the same exercise earlier in the day. The results add to growing evidence that when we exercise may alter how we benefit from that exercise.
Scientists have known for some time that the chronology of our days influences the quality of our health. Studies in both animals and people indicate that every tissue in our bodies contains a kind of molecular clock that chimes, in part, in response to biological messages related to our daily exposure to light, food and sleep.
These cellular clocks then help to calibrate when our cells divide, fuel up, express genes and otherwise go about their normal biological work. Tuned by our lifestyles, these clocks create multiple circadian rhythms inside of us that prompt our bodies’ temperatures, hormone levels, blood sugar, blood pressure, muscular strength and other biological systems to dip and crest throughout the day.
The Best Time of Day to Exercise
Circadian science also shows that disrupting normal, 24-hour circadian patterns can impair our health. People working overnight shifts, for instance, whose sleep habits are upended, tend to be at high risk for metabolic problems such as obesity and Type 2 diabetes. The same is true for people who eat late at night, outside usual dinner hours. More encouraging research suggests, though, that manipulating the timing of sleep and meals can improve metabolic health.
But much of this research focused on when we eat or go to bed. Whether, and how, exercise timing might influence metabolic health has been less clear, and the results of past experiments have not always agreed. Some suggest that morning workouts, for instance, amplify fat burning and weight loss.
But those experiments often manipulated the timing of breakfast and other meals, as well as exercise, making it difficult to tease out the particular, circadian effects of workouts. They also typically involved healthy volunteers, without metabolic problems.
A much-discussed 2019 study, on the other hand, found that men with Type 2 diabetes who completed a few minutes of high-intensity interval sessions in the afternoon substantially improved their blood-sugar control after two weeks. If they did the same, intense workouts in the morning, however, their blood-sugar levels actually spiked in an unhealthy fashion.